There have been technologies for searching for corresponding points from among multiple images. One of the methods of searching for corresponding points is block matching, with which matching of blocks of a certain size included in the images is performed. As a block matching method, as described, for example, in JP-A 2008-234465(Kokai), a maximum absolute difference (MAD) may be used. According to this method, block matching that is robust in lightness variation can be realized. The MAD is weak in noise, but by linearly combining the sum of absolute differences (SAD), noise robustness can also be ensured.
With the conventional technologies, however, matching can be successfully conducted if the blocks include characteristic image patterns, but it may fail if the blocks do not have anything particularly characteristic and their lightness is flat. For this reason, a technology that can realize block matching with high accuracy has been desired.